Telephone system



Nov. 6, 1928. 1,690,210

R. L. STVOKELY TELEPHONE SYSTEM File y 5, 1927 4 Sheets-Sheet 1 No v. 6, 1928.

R. L. STOKELY TELEPHONE SYSTEM Flle y 5 1927 4 Sheets-Sheet R. L. STOKELY TELEPHONE SYSTEM Nov. 6, 1928.

Filed May 5, 1927 4 Sheets-Sheet 5 WAY L. 570mm WV/14W v Nov. 6, 1928.

t R. L. STOKELY TELEPHONE SYSTEM Filed May 5, 1927 4 Sheets-Sheet 4 I 4// ml EL4/fi Patented 'Nov. 6, 1 92 8.

UNITED iiSTA TES RAY L. sTOKELY, o irLoR L iAnx, NEW YORK, ASSIGNOR '10 BELL TELEPHQNELA-BO- RAToRIEs, INCORPORATED, 013 NEW YORK, N. Y., A CORPORATION OF NEW YORK. I

' TELEPHONE SYSTEM.

1 Application filed May 5,

This invention relates to automatic tele phone cxchangesystems and more particularly wherein tie lines are divided intorelatively large groups, say 1200 lines each. In order to use switches havinga capacity for 200 linesit'becomes desirable to slip the line multiple from switch to switch to more uniformly. distribute the hunting time. This is a costly and troublesome expedient! To avoid this multiple slipand retain-the advantages of the i largergrouping it is proposed to employ two separator groups of lOO pointswitelles for normally serving two groups of 100 lines, the switches havingtwobanks of fine levels each and two simultaneously operable" sets of brushes. Since the maximum sub group hunting operation takes only five vertical steps it not necessary to slip the multiple,

The number of switches in thesetwo groups may beselected to care for the greater part of the traffic for the 200 lines." To handle the overflow calls in the more. busy priods a group of 200 point switches is provided which serve any, line in thegroup of200 when the firstchoice switches are all busy. I

In the drawings Figs. 1 and 2 taken togetlier comprise a diagram showing both the a regular and overflow finders: serving a group of200 lines. a

Figs, Band E4ithken together illustrate the details'ot a line .finder jswitch; and its controlling circuits.

Considering thediagram in Figs. 1 and 2, agroup of 100 subscriberslines appear in the multiple terminals of a group of line vfinder switches 100.: flhe group 100 comprises 10 line finders $1111, 2102, 103,. etc, each having a capacityr for "1.0 O"1ines, fEach of ,invention is applicable to a system using ste -bystep linefinder switches and 1927. swam. 188,918.

these switches has two separateline banks and two sets, of brushes each bank having 5 levels 0t terminals. Vlheline finders are provided withgroupselecting commutators 141, 142, 1 13, etc, and also with start wire controlling relays 121, 122, 123, etc. i i

The second group of 100 lines in the major group of 200 appeal-sin the multiple tenninals of a plurality of line finders 110. The

group 110 is made upof line finders 11.1,

112,113, etc, of the same construction as those illustrated in the group 100. These finders also have group hunting commuta- ,tors 151,.152, 153,.and start wire controlling relays 131, 132, and 138, etc; Normally the callsoccurring-in the line -groups are served by their finder switches 100 and 110. S nce, however, theremay not be enough of these'switches to handle the trailic in busy hours, a .group of overflow finder switches 200 is provided {to take care of all overflow calls in either of; the 100 line groups. To this .end the overflow finders 201,- 202, 203, etc, are 200 point switcheseach 7 having two 100 point banks and two sets of brushes. The lines in both 100 line groups are connected-as illustrated to the multiple terminals of the overflow finders 200. The overflow finders are likewise equipped :with eommutators .231, 232, 233, each having 10 segments instead of 5 and start wire con trolling relays 221,222 and 223, etc. 1

The armatures 241 to 2115 inclusive are 0011- i trolled by a make busy relay associated with the findersof one line group and which operates whenever all finders in that group. are busy. Similarly the armatures 251fto 255 inchisive are controlled by a group busy relay associated with the line findersotthe other. 100 line group. 1 I

Eachgroup of 100 lines has 5 different start wires, one for each subgroup of 20 lines for QXample. The start wires ot'the first 101) line group enter at point-e114 to 118 inclusive,

Likewisethe start wires for the second .100

line group enter at points 124,- 125, etc. I-ta call arises in the'first sub-group of 20 linesthe startcircuit extends over conductor 114, normal contact of relay 121 (if the first line finder, 101 is idle) conductor126 to. the start relay not shown. It the first finder 10 1 is busy thestartwire extends through the front 7 contact-of relay 121 and thenceoverthe back fill contact of relay 122 (if the second finder 102 is idle) to the start relay of that finder. If, however, both finders 101 and 102 are busy at the time, the start wire extends through the front contacts of relays 121 and 122 and thence over conductor 127, armature 2 11 and its back contact, conductor 22%, thence over the back contact of relay 123 (if the third finder is idle) to the start relay. It will he noted that the start wire after extending through two busy finders in the group passes through the contact 24.1 of the make-busy relay before it is extended to a subsequent finder. This to make sure that there is an idle finder in the group for if all finders are busy it will be useless to extend the start wire through the controlling relays of all finders in the series. By analyzing the start wire it will be found that after being extended through each succeeding pair of switches a collective test is made through the contacts of the make busy relays to determine whether there is an idle finder in advance of the point to which the start wire has been extended. The extension of the start wire will continue so long as each test reveals an idle finder somewhere beyond. If, however. any one of these tests shows that all finders beyond are usy the extension ceases and an overflow finder is setin motion. If all finders are busy the start wire is extended as explained over conductor 127 and thence through the armature 241 of the make busy relay and its front contact to the armature and normal contact of relay 221 (if the finder 201 is idle) and thence to the start relay of finder 201. Thus, whenever a, call originates in the group 100 and all the finders are busy the start wire after testing out two finders is extended to the overflow group and initiates the operation of one. of these overflow finders to take care of the call. It the first finder 201. in the overflow group is busy the start wire leads through the front contact of relay 2 1 to the relay 222 of the next switch. In like manner the start wire is extended from switch to switch in the overflow group until an idle finder is encountered.

Likewise a call originating in any sub group of lines in the second group of 100 causes the extension oi the start wire over one of the leads 121;. 121) to determine if there is an idle finder in the group 110. The start wire 12d for instance leads through the armature and front contacts of rela 1.31 and 132 it both finders 111 and 112 are busy thence over conductor 131 to the armature 251 on the make busy relay associated with the second group. of 100 lines. It some succeeding finder in group 110 is idle the armature 251. will be resting on its back contact and the start wire returns over conductor to the armature of relay 133. If however, the finders are all busy in this groupthen the make u y relayis operated and the start. wire now leads over the armature 251 and its front contact to the armature of relay 222.

From this it will he noted that the first, third, fifth, etc, overflow finders are preferred when a call overflows from the first group of 100 lines and that the second, fourth, sixth, etc., overflow finders are preferred for calls overflowing from the second group of 100 lines. Obviously as many finders both in the regular and overflow groups may be provided as is necessary to handle the tratlic.

Fig. 3 shows one of the regular line finders serving a group of 100 lines. This switch has two sets of line brushes 5310 and320 and a set of test brushes 318 all mounted on thesame shaft. The ln'nshes 310 cooperate with the bank 306 having levels of lines, each level :wconnnodating lines. Likewise the brush set 320 cooperates with a bank at)? having 5 levels of lines. The testhrushes 318 cooperate with a. separate test bank 305. At each vertical step of the brush shaft, the brushes 320, 319 and 318 are positioned opposite the correspomling levels of lines in the respective banks. In this way for each vertical step the switch chooses two levels of lines or a subgroup of lines. The lines 300 and 301 are seen to appear in corresponding levels of the two banks 306 and 307.

The switch is also equipped with a. vertical group hunting commutator 321 and a connnutator brush 322 the purpose being to enable the select-ion of two levels of lines, one of which contains a calling line.

The controlling relays shown to the right of the broken line in Fig. 4 are common to the finder F and all other finders serving the same group of lines. Relays 400 and 401 are the group busy relays previously referred to and in fact are the relays which control the armatures 241 to 245 inclusive shown in Fig. 2 of the diagram.

T he relays shown at the left of the broken line in Fig. 4 are common to the entire group 01 200 lines and certain of these relays relate to the overflow finder switches as will be explained in greater detail hereinafter.

There is a group relay 303 provided for each 40 subscrihers lines. The upper winding of the relay 303 relates to 20 lines whereas the lower winding relates to another 20 lines. These group relays, when energized by a calling condition on any one of the related lines, cause the line finder switches to perform. their line hunting operations.

In describing the detailed operation of the switch assume that a subscriber at: substation A initiates a call. The line relay 302 operates in an obvious circuit and completes a circuit from ground through the left contact of relay 106, conductor 4:07, contact of relay 802, upper winding of group relay 303 to battery. Relay 303 through its inner upper contact places groundq'iotential' on the commutator segment 323 corresponding to the levelcontaining line 300Iin the bank 306 andalso containing the line 301in the bank 307 Relay 303, also closes a start circuit from the grounded conductor 407, contact of relay 302, upper contactsof relay303, conductor.

Y circuit of the magnet to give the switch its, next step. In this way the brushes are advanced from level to level to search for the; levelofline-s containing the calling line. 4 Since the calling line'300 is assumed tov be in the first level a circuit is closed over thetive levels. The Y left contact severs .t 1e operating-circuit of a relay 313 whichreleases in turn-opening the circuit of the magnet 31 5. Magnet315closes 324, normal, contact of start wire control relay 311, winding of the start relay 312 .to

battery. Relay 312 in operating places ground .on the sleeve aconductor 325 -ofthe trunk 317 leading to the first selector.

Relay 312 also operates the relay 313 in, a circuit from ground through the outer left contact of relay 312, contact of the vertical;

magnet 314, left contact of therotary maginet 315, rightwinding of relay 313, contact of relay 311 ,tobattery. Relay 313 closes a. circuit for the vertical magnet 31 1jfrom battery through the contact of, relayl311, winding of magnet 314, outer right back contact of relay 310, contact/of relay 313 to ground at the contactof relay 312. The mag net 314 operates the brush shafts and steps the brushes 318, 319 and 320 in operative relation to the first level of terminals. Italso advancesthe commutator. brush 322 into engagement with thefirst segment -Mag net 314 at itscontact opens the circuit of relay 313 which releases and opens the circuit of the magnet permitting it to release. Magnet 314 again closes the circuit ofrelay 313 which is arranged tooperate and reclose; the

commutator brush; 322 to hold therelay 313 energized at the end of the first step thus preventing the, reclosure of the stepping" magnet circuit. ,Thefholdin circuit for relay 313 may betraced from contact of relay 311, right Winding of'relay 313,1eft contact of the rotary magnet2315,

left winding of relay 310, brush 322 to the grounded segment 323. The relay 310 operates slowly, to allowvan interval between the vertical and rotary stepping movements.

The relay "310 closes a locking circuit for itself to battery, through the cont-act of relay ing of said magnet, the outer right front con t-actrof relay 310, contact of relay, 313,:to groundat the contact of relay 312-. 1 Magnet 315 advances the brushes into engagement with the first set of terminals in the respec et 315 in openingits attery over A the 7 its contact, reclosing the circuit of relay 313 which operates and again closes the operating circuit of themagnet. In thijsway the brushes of the finder areadvanced from terminal to terminal in search ot'thecalling line.

The'test for the calling line is made by the "relays 308' and 309. If the calling lineislin the upper bank306 relay 308 operates and incidentally causes theoperation of'relay 309, whereas if thecalling line is in the lower bank 307 relay 309 operates. One branch of the. test circuit may be traced from ground atthecontact of relay 312,1eft winding of relay 313, inner right hand normal contact ofirelay 308, inner left back'contactof; relay 309, right winding of relay 308, to the upper test brush 318. The other branchiof the test circuit after passing through the left winding of relay 313 leads through the-backbontact of relay 311, left winding of relay 309 to the lower test brush 308. Since line 300 is the one calling, the first mentioned test cira cut is closed through the upper brush 318 and the correspondng terminal, inner contact of line relay 302, winding of the cut-oft relay 304to battery. Relay 308operatesin this circuit and relay 313 is held operated to pre-- vent any further stepping by the magnet 315. Relay 308 in operating closes acircuit for the relay 309 from battery through the rightwinding of the latter relay, outer rightcontact of relay 308, rightfront contactof relay 312 to groundat the upper contact of the oil'- normal spring combination 326.. Relay 309 operates the relay 311 in -ai circuit frombattery through the right'winding' of relay 311,

outer right front contact of relay 309 "to ground at the upper contact of springs=326, Relay 311 extendsthe sleeve cond uctor 325 from the first selector through to the sleeve conductor of the line 300'. lliiscircuitinay betraced from conductor 325, left frontcontactfof relay 311, inner right iirontcontact.

vof relay 308, upper test brush 318 'to the sleeve conductor of the line. The cut-oil relay 304 is inaintained operated inthis jcir}.

cuit. a r a g: j Relay 311 transfers the start circuit324 to the next switch as illustrated in Figs. 1 and 2, and'releases relays 312, 313 and 310; Rel'ay isjslow to releaseto provide ani'nterval for ground potential to be'placed on the conductor 325 at the first selector switch in the usual manner. "The relay 308 is maintained energized froin battery through its left winch mg and contact, normalcontact of relay 310' to ground at the 1 spring combinationT326."

Relay 309 is heldin a circuit-from battery through its right winding and front contact,

outer left contact of relay 311 to the sleeve conductor 325' The relays 308 and 309 extend the tip and ring conductors of the trunk 317 through to the "uppersetozt brushes319 resting'on thefterminals in theicallin'g line 7.

When it is desired to release the connection the ground potential is removed from corn ductor 325 and relay 309 releases. The release magnet 316. now operates in the cir cuit from battery through the winding of said magnet, closed contact of the spring combination 326, inner left contact of relay 310, outer right back contact of relay 3th, outer right contact of relay 3.12 to ground through closed contact of spring combination 326. \Vhen the switch is restored the olfnormal spring combination 320 is opened and the release n'iagnet i520 deenergizes. Relays 308 and 304 are also released.

Had the call originated on the subscribcrs line 301, the same group relay 303. is operated over its upper winding. Should a call originate on any one of twenty other lines (not shown in Fig. 3) groum'l potential is connected to. the conductor 32? and the relay 303 operates over its lower winding to extend the start wire 328. The start wire 328 starts a line finder in operation in the manner already explained.

The equipment shown to the left of the broken line in Fig. 4 is common to a group of 200 lines and accordingly relates to the overflow finders. One of the overflow finders has been illustrated by the broken rectangle 420. The relay 421 within this rectangle is the start wire controllngrelay corresponding to the relay 311 in Fig. 3.

The relays 402 and 403 relate to the group of 100 lines served by the finder switch F.

- A circuit may be traced for these relays from battery through the winding of relay 402 thence through normal contact of relay. 311 tot ground through the winding of relay 403. There will also be a parallel circuit for these relays extending through normal contacts of each of the relays corresponding to relay 311 for the remaining line finders of the group. As long as any line finder in the group is. idle the relays 402 and 403 are held operated.

"When all finders of the group become busy all parallel paths for the relays 402 and 403 are opened and theserelays will release. The group busy relays 400 and 401. now operate in a circuit from battery throughtheir Windings through back contacts of relay 403 and 402 to ground. The group busy relays shift the start wire as explained in connection with Figs. 1 and 2-, to the overflow finders.

Should either positive or negative potential he accidentally applied to the start wire the relays 4.02 and 403 are released in different combinations according to the point at which the potential is applied. lVith either relay released and the other relay operated, a circuit may be traced from signal lamp 405.

The relays 408 and 409 and the lamp 414 serve the same. purpose as relays 4.02 and 403 and lamp 405 with respect to the group of When all 01 the overflow finders are busy and both relays 408 and 40$) release a circuit is closed from battery through the winding in relay 406 to ground through the back contacts of relays 408 and 400. Relay 400 operates and disconnects its grounded arinatures from the start conductors 407 and 415. if a call exists in the group while all of the overflow finders are busy and ground potential occurs on the start conductor 4:10, the relay 410i; operated through the right contact of relay 400. (clay 410 closes an obvious circuit forrelav 411 which locks through the key 1 1?.

Relay 411 lights the signal lamp 4 ii and abo closes an obvious circuit for relay 412 so long as relay 410 remains energized. llclay 41L removes battery potential from the conductor 418 which controls all relays similar to relay 421.

\Vhat is claimed is:

1. In combination, two groups of lines. each divided in sub-groups. two finder switchem each serving one of said groups as first choices means for operating one of said finders to simultaneously select a plurality of snbgroups, means for further operating the finder to select a line in one of the selected sub-groups, a third finder serving all of the lines in both said groups, and means for operating said last finder to select a sub-group of lines and a line therein when the first choice finder is busy.

2. In combination, first and second groups oi lines divided in subgroups, a plurality oi finders serving the first group as first choice finders, a plurality of finders serving the sec ond group as first choice finders, means for operating any one of said finders to simultaneously select a plurality of sub-groups. means for further operating the finder to select a line in one of the selected subgroups, a. plurality ot third finders serving all of the lines in both said groups, and means for operating said last finders to select a sub-group of lines and an individual line therein when the first choice finders are all busy.

3. In combination, first and second groups of lines divided in. sub-groups, a plurality of finders serving the first group as first choice finders, a 'ilurality oi finders serving the second group as first choice finders. means dependent on the location of the calling line in a group for determining the order in which the finders are started. means for operating any finder to choose a plurality of sub-groiuis simultaneously, means for further operating: the finder to select a line in one of the chosen sub-groups, a plurality of second choice tinders serving all of the lines in both said groups, and means for operating any one oi said last finders to select a calling line when all of the first choice finders are engaged.

4. In a telephone system. first and second groups of lines divided in sulii-groups, a series of finder switches serving the first group as til Hill

first choice, a series of finder switches serving the second group as first choice, a start wire for each series, means for extending the start wire from one finder to the next when busy, means for testing collectivelyall finders in advance of the extended start wire,.and a a group of overflow finders'serving as second choice to the lines in both groups.

5. In a telephone system, agroup of lines, a series of finder switches serving said lines, a start wire for said finders, means to extend the start wire from switch to switch when busy, and means for testing collectively all switches in advance of the extended start a wire to determine if there bean idle one.

, 6. In a telephone system, a group of lines, a series of finderswltches serving said lines, a

start wire for said finders, means to extend the start wire from switch to switch when 20 busy, and means torepeatedly test all switches collectively in advance of the eXtended sta-rt wire to determine if there be an idle switch.

7. In combination, a plurality of groups of lines, finder switches for each group serving as first choice switches for said groups, levels of terminals in said switches in which the lines appear, a plurality of sets of brushes for each swltch, means for advancing all brush sets on any one of said switches into engagement v RAY L. STOKELY, 

